View Full Version : What is the null and alternative hypothesis?

02-14-2011, 03:37 PM
In making aluminum castings into alternator housings, an average of 3.5 ounces per casting must be trimmed off and recycled as a raw material. A new manufacturing procedure has been proposed to reduce the amount of aluminum that must be recycled in this way. For a sample of 35 castings made with the new process, data file XR10111 lists the weights of aluminum trimmed and recycled. Based on the sample data, and using the 0.01 level, has the new procedure significantly reduced the average amount of aluminum trimmed and recycled? Identify and interpret the p-value for the test.
i think it is:

Null Hyp: Mu1 = Mu2
Alternate hyp: Mu1 does not equal to Mu2

02-14-2011, 07:38 PM
H0 is good. Think "status quo" when creating these.

Ha might be okay, but you REALLY think it should bd <, so you may as well check that direction.

However, not everyone likes this. some feel you should ALWAYS test against NOT EQUAL before you test against a specific direction. Maybe they are right. Opinions vary.